Automatic gain control receiver



3]@1, ANDERS 4 2,@46g144' AUTOMATIC GAIN CONTROL RECEIVER Filed Dec. 17,1932 OTH- BY/fm ATTORNEY Patented June 30, 1936 'airco lsiaras PATENTOFF-HCE'.

AUTOMATIC GAIN CONTROL RECEIVER Germany Application December 17,issaseriai No. 647,719 In Germany January 22, 1932 7 Claims.

My present invention relates to a novel gain control means for receiverarrangements using indirectly heated tubes.

In high-grade receiver sets for radio communication it is desirable toprovide anti-fading (fading regulation or compensation) means so as toneutralize liuctuations in the Volume. Arrangements of this kind areknown in the art, and they are based upon the fact that, upon the risingof the signal voltage at the second detector grid, the plate current ofthe second detector is caused to increase while its plate potentialdecreases as a result of the growth in potential across the plateresistance. This amplitude dependence is usually utilized for theregulation of the grid biasing potential of the rst radio frequencyamplier tube.

Customary circuit schemes of this type, however, involve the drawbackthat the plate voltage of the end, or power, tubes is reduced by anamount equal to the biasing voltage employed for fading compensation.The present invention discloses a circuit scheme which is free from thesaid drawback. One exempliied embodiment of the invention is shown inthe drawing.

In parallel relation to the output of the second detector tube l is ahigh-ohm voltage divider consisting of the high-ohm resistances 2 and 3.Part of the voltage at the tube I is fed to the grid of the amplifiertube 4 through lead 5. Inasmuch as the said grid would be biased as aconsequence, it is necessary to introduce a negative compensatingvoltage. Contradistinct to schemes known in the earlier art, this ishere insured by that the emissive layer, coat, or electrode of theamplifier is fed with a positive biasing potential from a potentiometerconsisting of the resistances 5 and E, the said potentiometer beingconnected in parallel to the source of filtered direct current.

This arrangement rst has the shortcoming that between theelectron-emissive layer and the filament 6 there may prevail arelatively high potential difference which may be harmful for the tube.It is thus necessary to preclude this risk by the arrangement upon theline-supply transformer of a distinct heating winding. With unchangeddimensions of the network-supply unit compared with that used in formerarrangements, it is feasible to obtain higher plate voltage for thepower tube in a circuit scheme according to this invention, in spite offading regulation.

In order to insure more intensive or eiiicient regulation it would bepossible to act upon the grid biasing potential of theintermediate-frequency amplier tube 'l conjointly with the use (Cl. Z50-20) of a similar grid biasing voltage in the irst radio tube. Theinuence of diiierent tubes makes itself felt substantially only in thesecond detector tube. n order to secure optimum grid biasing voltages inthe tubes to be regulated the said detector tube must show a certainvalue of plate current. This value is obtained by the adjustment of thesecond detector grid biasing voltage by the aid of a potentiometer l0 orthe like, the variable resistor lil being connected between the grid andcathode of tube I.

What is claimed is:-

l. In combination, in a radio receiver, a radio frequency amplifierincluding a signal grid, cathode and anode, a rectifier including a tubeprovided with a grid, cathode and anode, means for coupling the rectiergrid to the amplifier' anode circuit for signal energy transfer, asource of direct current, a connection including a resistor from therectifier anode to a positive potential point of said source, therectiiier cathode being connected to a negative potential point of thesource, a path including at least two resistive portions connectedbetween the rectiiier anode and the said negative point, a directcurrent connection between the amplifier grid and a point intermediatesaid portions, at least two resistors connected across said sourcebetween said positive and negative points, a connection from theampliiier cathode to a point intermediate said two resistors, thepotential of the second intermediate point being substantially morepositive than that of the rst intermediate point and the said negativepotential point to which the rectiiier cathode is connected, and aconnection from the amplier anode to said positive potential point ofsaid source.

2. In a receiver, as defined in claim l, a heater element in saidampliiier, a heater element in said rectier tube, a supply transformeradapted to be connected to a heating alternating current source, thetransformer including independent secondary windings for the ampliierand rectifier heater elements.

3. In a receiver, as dened in claim 1, a heater element in said amplier,a heater element in said rectiiier tube, a supply transformer adapted tobe connected to a. heating alternating current source, the transformerincluding independent secondary windings for the amplifier and rectierheater elements, a connection between the ampli- Iier cathode and itsheater winding, and a connection between the rectifier cathode and itsheater winding.

4. In a receiver as dened in claim 1, a Variable radio frequencyamplifier, first detector, inter-V mediate frequencyamplier and seconddetector, a source of direct current for energizing the anode circuitsof said amplifiers and second detector, a

Vpair of resistors connected between the second.

detector anode and the negative side of said source, an impedanceconnected between the positive side of said source and the seconddetector anode, a direct current connection between the grids of saidamplifiers and a point intermediate the said resistors, a second pair ofresistors con.- nected across said source, and a direct currentconnection between the cathodes of said amplifiers and a pointintermediate the said second pair of resistors which is at a positivevoltage with respect to the first point.

6. In a receiver as defined in claim 5, a connection between the cathodeof the second detector and the negative side of said source, said lastconnection including a. variable resistor for regulating the flow ofcurrent in the anode circuit of the second detector.

v'7. In a receiver as defined inV claim 5, said ampl'iers and .seconddetector including heater elements for the cathodes thereof, and aheating current supply transformer having one secondary

